Descent Into the Depths of the Earth is an adventure module for the Dungeons & Dragons (D&D) fantasy roleplaying game coded D1–2. It was written by Gary Gygax, and combines two previously published modules from 1978, the original Descent into the Depths of the Earth and Shrine of the Kuo-Toa. A sequel to the first two modules, Vault of the Drow, was also published in 1978. All of these D-series modules were produced for use with the 1st edition Advanced Dungeons & Dragons (AD&D) rules.